JP4869896B2 - Optical tomographic imaging system - Google Patents

Description

  The present invention relates to an optical tomographic imaging apparatus that acquires an optical tomographic image to be measured by OCT (Optical Coherence Tomography) measurement.

  Conventionally, when an optical tomographic image of a living tissue is acquired, an optical tomographic image acquisition device using OCT measurement is sometimes used. This optical tomographic image acquisition apparatus divides low-coherent light emitted from a light source into measurement light and reference light, and then reflects or backscatters light from the measurement object when the measurement light is applied to the measurement object. The light and the reference light are combined, and an optical tomographic image is acquired based on the intensity of the interference light between the reflected light and the reference light. Hereinafter, the reflected light and the backscattered light from the measurement object are collectively referred to as reflected light.

  The OCT measurement is roughly divided into two types: TD-OCT (Time domain OCT) measurement and FD (Fourier Domain) -OCT measurement. In TD-OCT (Time domain OCT) measurement, reflected light corresponding to a position in the depth direction of a measurement target (hereinafter referred to as a depth position) is measured by measuring the intensity of interference light while changing the optical path length of the reference light. This is a method for obtaining an intensity distribution.

  On the other hand, the FD (Fourier Domain) -OCT measurement measures the interference light intensity for each spectral component of the light without changing the optical path lengths of the reference light and the signal light, and uses the obtained spectral interference intensity signal as a computer. In this method, the reflected light intensity distribution corresponding to the depth position is obtained by performing frequency analysis represented by Fourier transform. In recent years, it has attracted attention as a technique that enables high-speed measurement by eliminating the need for mechanical scanning existing in TD-OCT.

  Typical examples of the apparatus configuration for performing FD (Fourier Domain) -OCT measurement include an SD-OCT (Spectral Domain OCT) apparatus and an SS-OCT (Swept source OCT). The SD-OCT apparatus uses broadband low-coherent light such as SLD (Super Luminescence Diode), AES (Amplified Spontaneous Emission) light source, white light as a light source, and uses a Michelson interferometer or the like to generate broadband low-coherent light. After splitting into measurement light and reference light, irradiate the measurement light on the object to be measured, cause the reflected light and reference light that have returned at that time to interfere with each other, and decompose this interference light into frequency components using a spectrometer. Then, the interference light intensity for each frequency component is measured using a detector array in which elements such as photodiodes are arranged in an array, and the spectrum interference intensity signal obtained thereby is Fourier transformed by a computer to obtain an optical signal. A tomographic image is constructed.

  On the other hand, the SS-OCT apparatus uses a laser that temporally sweeps the optical frequency as a light source, causes reflected light and reference light to interfere at each wavelength, and measures the time waveform of the signal corresponding to the temporal change of the optical frequency. An optical tomographic image is constructed by Fourier-transforming the spectral interference intensity signal thus obtained with a computer.

  In the OCT apparatus, in order to obtain a result with higher resolution and higher image quality, it is necessary to widen the wavelength of the light source and increase the number of data points accordingly. However, since the SD-OCT apparatus generally detects interference light for each wavelength using a detector array in which elements such as photodiodes are arranged in an array, the number of data points is limited by the number of elements in the detector array. End up. Attempting to increase the number of detector array elements in order to increase the number of data points is not preferable because of an increase in cost, a decrease in manufacturability, and a decrease in measurement rate. On the other hand, in the SS-OCT apparatus, in order to increase the number of data points, for example, when the frequency sweep cycle of the light source is constant, the sampling frequency of the circuit that converts the photocurrent signal from the detector into a digital value is increased. Therefore, it can be easily realized at a low cost while keeping the measurement rate high.

  In the various OCT measurements described above, it is known to use measurement light having a wide spectrum width in order to improve spatial resolution (see Patent Document 1). As a light source that emits light having a broad spectrum width, Patent Document 1 discloses a plurality of light sources that emit light having different spectral bands, and light emitted from each light source is combined by an optical coupler. A method of emitting a single light wave is disclosed.

In SD-OCT measurement, Patent Document 2 discloses a method of forming a continuous spectrum by combining lights of a plurality of gain media having overlapping wavelength bands. As a method for forming a continuous spectrum by multiplexing in SS-OCT measurement, Patent Document 3 discloses a configuration including a plurality of wavelength scanning light sources each having a gain medium and a wavelength selection element. Document 4 discloses a configuration in which light from a plurality of gain media is simultaneously controlled by one wavelength selection element.
JP 2002-214125 A JP 2001-264246 A JP 2006-47264 A US Pat. No. 6,665,320

  As described above, when combining and using light from a plurality of light sources in order to obtain a high spatial resolution, the conventional SS-OCT apparatus has a single detector, and therefore light of different wavelengths from the plurality of light sources. Are emitted at the same time and irradiated onto the measurement object, there is a problem that interference information by these plural lights is mixed and cannot be detected.

  For this reason, the devices described in Patent Document 3 and Patent Document 4 are configured such that the wavelength of light incident on the detector becomes one by controlling the light source or using a switching element or the like. However, in such a method, although broadband light can be used as measurement light, it takes time to irradiate light in the entire wavelength band of the measurement light, which causes a problem that the measurement rate decreases.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical tomographic imaging apparatus capable of acquiring a high-resolution tomographic image at high speed.

The optical tomographic imaging apparatus of the present invention includes a first light source that emits first light whose wavelength is repeatedly swept within the first wavelength band, and a second light source having a wavelength band different from the first wavelength band. A second light source that emits a second light whose wavelength is repeatedly swept within a wavelength band, and a part of the first light sweep and a part of the second light sweep are performed simultaneously. A light source unit,
Light splitting means for splitting the first light and the second light into first and second measurement light and first and second reference light, respectively;
The first and second reflected light and the first and second reflected light that are reflected from the measurement object when the measurement object is irradiated with the first and second measurement lights divided by the light dividing means A combining means for respectively combining the reference light of
First interference light detection means for detecting, as a first interference signal, first interference light generated when the first reflected light and the first reference light are multiplexed by the multiplexing means;
Second interference light detection means for detecting, as a second interference signal, second interference light generated when the second reflected light and the second reference light are multiplexed by the multiplexing means;
An optical tomographic imaging apparatus comprising: a tomographic image processing unit configured to generate a tomographic image of the measurement target using the first and second interference signals detected by the first and second interference light detection units. There,
The reflected light or the interference light from the measurement object is emitted to the first interference light detection means side when the wavelength of the reflected light or the interference light is within a third wavelength band, When it is within a fourth wavelength band that is distant from the third wavelength band, the light is emitted to the second interference light detection means side, and the second wavelength band between the third wavelength band and the fourth wavelength band is emitted. 5 having a wavelength division unit that emits light to the first interference light detection unit side and the second interference light detection unit side,
The first wavelength band and / or the second wavelength band includes at least a part of the fifth wavelength band, and the tomographic image includes the first light source and the second wavelength band. While light having a wavelength within the fifth wavelength band is emitted from one of the light sources, only the first interference signal or the second interference signal based on the light emitted from the one light source It is what is produced | generated using.

  The tomographic image processing means emits light from one of the first light source and the second light source as an interference signal while light having a wavelength in the fifth wavelength band is emitted from the one light source. Only interference signals based on the light being used may be used.

  Further, the interference light detection means is emitted from the one light source while light having a wavelength within the fifth wavelength band is emitted from one of the first light source and the second light source. Only the first interference signal or the second interference signal based on the light that is present may be detected.

  While the light source unit emits light having a wavelength within the fifth wavelength band from one of the first light source and the second light source, only the one light source emits the fifth wavelength band. The light of the inside wavelength may be emitted.

  The light source unit emits light from only one of the first light source and the second light source while emitting light having a wavelength within the fifth wavelength band from one of the first light source and the second light source. It may be a thing.

  The light source unit emits light having a wavelength within the third wavelength band from the first light source and simultaneously emits light having a wavelength within the fourth wavelength band from the second light source during a predetermined time period. While the light having the wavelength in the fifth or fourth wavelength band is emitted from the first light source, the light is emitted only from the first light source, and the first light source emits light. While light having a wavelength within the fifth or third wavelength band is emitted from two light sources, light may be emitted only from the second light source.

  A part of the first wavelength band and a part of the second wavelength band may overlap.

  The tomographic image processing unit connects the first interference signal and the second interference signal obtained by the first interference light detection unit and the second interference light detection unit and having a part of overlapping wavelength bands. Thus, one interference signal may be formed, and a tomographic image may be generated based on the interference signal.

  The wavelength division means may be a wavelength division multiplex coupler.

  The light splitting unit and the multiplexing unit may be provided for each of the first light and the second light.

  According to the optical tomographic imaging apparatus of the present invention, when the reflected light or the interference light from the measurement object has a wavelength of the reflected light or the interference light within a third wavelength band, 1 to the interference light detection means side, and in the fourth wavelength band apart from the third wavelength band, emits to the second interference light detection means side, and the third wavelength A wavelength division unit that emits light to the first interference light detection unit side and the second interference light detection unit side when within a fifth wavelength band between the band and the fourth wavelength band; Therefore, while the light of the third wavelength band and the light of the fourth wavelength band are respectively emitted from the first light source and the second light source, the light emitted from each light source is wavelength-divided. The wavelength is divided by the means and received by the interference light detection means. Even if the measurement target is irradiated, multiple interference signals due to the multiple interference lights generated at this time will not be mixed, and multiple interference signals can be obtained for each light at the same time. The rate can be improved. Here, “for each light” means for each light in the same wavelength band.

  In addition, while light having a wavelength within the fifth wavelength band is emitted from one of the first light source and the second light source, the first light source based on the light emitted from the one light source. Since the tomographic image is generated using only one interference signal or the second interference signal, the light in the fifth wavelength band, which is difficult to divide the wavelength strictly by the wavelength dividing means, is emitted. Even if it is a case, the several interference signal by several interference light is not mixed, and several interference signal can be obtained simultaneously for every light. For this reason, it is possible to detect interference signals over a wide band and continuous spectrum, and to acquire a high-resolution tomographic image at high speed.

  Furthermore, in the conventional apparatus including a plurality of light sources and a plurality of gain media, it has been necessary to perform control in synchronization so that the wavelength of light incident on the detector becomes one. According to the converting apparatus, such control is unnecessary, and the apparatus can be simplified. Further, in the optical tomographic imaging apparatus of the present invention, each interference light detection means can be optimized according to the wavelength band of each light, so that the detection accuracy in each interference light detection means is improved and acquired. The resolution of the tomographic image can be improved. Furthermore, the components used for the interference light detection means do not need to support broadband light, and only need to support the wavelength band of each light. Can be used, and the device configuration becomes easy.

  Hereinafter, an embodiment of an optical tomographic imaging apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an optical tomographic imaging apparatus 100 according to the first embodiment of the present invention. The optical tomographic imaging apparatus 100 acquires, for example, a tomographic image of a measurement target such as a living tissue or a cell in a body cavity by the above-described SS-OCT measurement using a Mach-Zehnder interferometer.

  The optical tomographic imaging apparatus 100 includes a light source 10a that emits a laser beam La that is swept at a constant period within a wavelength band Δλa (1295 nm to 1345 nm), and a wavelength that is a wavelength band Δλb (1255 nm to 1305 nm). A light source unit 10 having a light source 10b that emits a laser beam Lb that is swept at a constant period, a multiplexing unit 2 that combines the light La and Lb emitted from the light source unit 10, and a light La And light Lb are split into measurement light L1a and reference light L2a, measurement light L1b and reference light L2b, respectively, and measurement light L1a and L1b incident on port a are emitted to port b and then to port b A circulator 4 that emits the incident reflected lights L3a and L3b to the port c, a wavelength division unit 5a that divides the reflected lights L3a and L3b, and a wavelength division unit that divides the reference light L2a and the reference light L2b. 5b, the multiplexing / demultiplexing means 6a for multiplexing the reflected light L3a and the reference light L2a, the multiplexing / demultiplexing means 6b for multiplexing the reflected light L3b and the reference light L2b, and the reflected light L3a by the multiplexing / demultiplexing means 6a. When the reflected light L3b and the reference light L2b are multiplexed by the multiplexing / demultiplexing means 6b, the interference light detecting means 40a that detects the interference light L4a generated when the light and the reference light L2a are combined as an interference signal. Interference light detection means 40b for detecting the generated interference light L4b as an interference signal, and tomographic image processing means 50 for acquiring a tomographic image of the measuring object S using the interference signals detected by the interference light detection means 40a and 40b. ing.

  Note that the measurement light L1a, the reference light L2a, the reflected light L3a, and the interference light L4a are based on the light La and are light in the same wavelength band as the light La. Further, the measurement light L1b, the reference light L2b, the reflected light L3b, and the interference light L4b are based on the light Lb and are light in the same wavelength band as the light Lb.

  The light source unit 10 includes a light source 10a that is a wavelength swept light source that emits laser light La that is swept intermittently and repeatedly within a wavelength band Δλa (1295 nm to 1345 nm), and a wavelength band Δλb (1255 nm to 1305 nm). And a light source 10b which is a wavelength swept light source for emitting laser light Lb whose wavelength is swept intermittently and repeatedly.

  The light source 10a of the light source unit 10 includes a semiconductor optical amplifier (SOA) 11a, which is a gain medium, wavelength selection means 12a including an FFP-TF (Fiber Fabric Perot-Tunable Filter), a semiconductor optical amplifier 11a, and a wavelength. It is mainly composed of an optical fiber 13a which is connected to both ends of the selection means 12a and constitutes a ring-shaped resonator.

  The semiconductor optical amplifier 11a has a function of emitting weak emitted light to the optical fiber 13a connected to one end side by injecting a driving current and amplifying light incident from the optical fiber 13a on the other end side. Yes. The semiconductor optical amplifier 11a is composed of, for example, an InGaAsP element having a light emission band at a wavelength of 1250 nm to 1350 nm. The semiconductor optical amplifier 11a causes laser light to oscillate in a ring-shaped resonator. The laser light is branched by an optical coupler 14a having a branching ratio of 10:90 connected to the optical fiber 13a and guided by the optical fiber FB1a. And emitted as light La to the outside. The wavelength selection unit 12a is configured to change the wavelength of light to be transmitted at a constant period within the wavelength band Δλa (1295 nm to 1345 nm).

  The light source 10b also has a configuration similar to that of the light source 10a, and a semiconductor optical amplifier 11b as a gain medium, wavelength selection means 12b made of FFP-TF, and a ring-shaped resonator connected to both ends thereof. The optical fiber 13b. The semiconductor optical amplifier 11b is also composed of an InGaAsP element. The laser light oscillated in the resonator of the light source 10b is branched by an optical coupler 14b having a branching ratio of 10:90 connected to the optical fiber 13b, guided by the optical fiber FB1b, and emitted as light Lb. In the light source 10b, the wavelength selection unit 12b is configured to change the wavelength of light to be transmitted at a constant period within the wavelength band Δλb (1255 nm to 1305 nm).

  The state of the wavelength sweep of the light sources 10a and 10b is shown in FIG. 2A, and the spectra of the light sources 10a and 10b are shown in FIG. 2B with La and Lb, respectively. The light source 10a performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλa (1295 nm to 1345 nm). The light La is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. The light source 10b performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλb (1255 nm to 1305 nm). The light Lb is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. Further, in the light source 10b, the sweep of the light Lb is started with a delay of 1 ms from the sweep of the light La in the light source 10a.

  The light La propagated through the optical fiber FB1a and the light Lb propagated through the optical fiber FB1b are combined by the optical combining means 2, emitted to the optical fiber FB31, propagated through the optical fiber FB31, and then to the light dividing means 3. Incident.

  The light splitting means 3 is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 90:10. The light splitting unit 3 splits the light La into measurement light L1a and reference light L2a, and splits the light Lb into measurement light L1b and reference light L2b. At this time, the light dividing means 3 divides at a ratio of measurement light: reference light = 90: 10. The measurement lights L1a and L1b are emitted to the fiber FB32, and the reference lights L2a and L2b are emitted to the fiber FB33.

  A circulator 4 is provided in the optical path between the light splitting means 3 and the probe 30, and the measurement lights L1a and L1b incident on the port a on the light splitting means 3 side of the circulator 4 are transmitted from the port b on the probe 30 side to the fiber. It is injected to FB34.

  The probe 30 guides the measurement lights L1a and L1b incident through the optical rotary connector 31 to the measurement target S and irradiates the same part of the measurement target S simultaneously. Further, the probe 30 guides the reflected lights L3a and L3b from the measurement object S when the measurement lights L1a and L1b are irradiated on the measurement object S. The probe 30 has a structure in which the fiber portion ahead of the optical rotary connector 31 is rotated by a motor (not shown), thereby scanning light circumferentially on the sample. A tomographic image can be measured. Furthermore, a three-dimensional tomographic image can be measured by scanning the tip of the probe 30 in a direction perpendicular to the plane formed by the scanning circle of the optical path by a motor (not shown). The probe 30 is detachably attached to the optical fiber FB34 by an optical connector (not shown). Of course, the shape of the probe tip and the scanning direction are not limited to this. For example, a configuration in which a high-speed scanning mirror is arranged at the fiber tip to perform two-dimensional scanning may be used.

  The reflected lights L3a and L3b emitted from the probe 30 through the fiber FB34 enter the port b of the circulator 4, and are emitted from the port c to the fiber FB35, and then enter the wavelength division unit 5a.

  The wavelength division means 5a is composed of, for example, a WDM coupler. Light having a wavelength of 1310 nm or more is emitted to the optical fiber FB36a side, light having a wavelength of 1290nm or less is emitted to the optical fiber FB36b, and light having a wavelength band of 1290nm to 1310nm. Injects on both sides. Specifically, the light in the wavelength band 1290 nm to 1310 nm is divided into the optical fiber FB36a side with a division ratio that changes from about 0 to 100%, and the optical fiber FB36b side changes into a division ratio that changes from about 100 to 0%. Divide by. For this reason, most of the reflected light L3a is emitted toward the optical fiber FB36a, and most of the reflected light L3b is emitted toward the optical fiber FB36b. On the other hand, a part of the reflected light L3a (a part of the light of 1295 nm to 1310 nm) is emitted to the optical fiber FB36b side (hereinafter, the reflected light L3a emitted to the optical fiber FB36b side is described as leakage reflected light L3as) and reflected. A part of the light L3b (a part of the light of 1290 nm to 1305 nm) is emitted to the optical fiber FB36a side (hereinafter, the reflected light L3b emitted to the optical fiber FB36a side is referred to as leakage reflected light L3bs). The multiplexing / demultiplexing means 6a is coupled to the optical fiber FB36a, and the multiplexing / demultiplexing means 6b is coupled to the optical fiber FB36b.

  On the other hand, the reference lights L2a and L2b separated by the light splitting means 3 are guided by the optical fiber FB33, and after the optical path length is changed by the optical path length adjusting means 7 provided in the middle of the optical fiber 33, the wavelength is changed. The light enters the dividing means 5b.

  Similarly to the wavelength division means 5a, the wavelength division means 5b is composed of, for example, a WDM coupler. Light having a wavelength of 1310 nm or more is emitted to the optical fiber FB37a side, and light having a wavelength of 1290nm or less is emitted to the optical fiber FB37b side. Light having a wavelength longer than 1290 nm and shorter than 1310 nm is emitted to both sides. That is, in the wavelength division 5b, most of the reference light L2a is emitted to the optical fiber FB37a side, and a part thereof is emitted to the optical fiber FB37b side (hereinafter, the reference light L2a emitted to the optical fiber FB37b side is leaked as reference light). L2as). Further, most of the reference light L2b is emitted to the optical fiber FB37b side, and a part is emitted to the optical fiber FB37a side (hereinafter, the reference light L2b emitted to the optical fiber FB37a side is referred to as leakage reference light L2bs). . The multiplexing / demultiplexing means 6a is coupled to the optical fiber FB37a, and the multiplexing / demultiplexing means 6b is coupled to the optical fiber FB37b.

  In the multiplexing / demultiplexing means 6a, the reflected light L3a and the reference light L2a are multiplexed, and the interference light L4a is divided into two and emitted to the interference light detection means 40a. In the multiplexing / demultiplexing means 6b, the reflected light L3b and the reference light L2b are multiplexed, and the interference light L4b is divided into two and emitted to the interference light detection means 40b. In the interference light detection means 40a and 40b, the halved interference light L4a and L4b are each subjected to balance detection using two light detection elements. By this mechanism, the influence of light intensity fluctuation can be suppressed and a clearer image can be obtained.

  The interference light detection means 40a and 40b have a function of photoelectrically converting the interference lights L4a and L4b, respectively, and detecting them as a plurality of interference signals ISa and ISb for the wavelength bands Δλa and Δλb of the lights La and Lb, respectively. . At this time, interference signals ISa and ISb for each spectrum of the light sources 10a and 10b are observed in the interference light detection means 40a and 40b. The interference signals ISa and ISb are output to the tomographic image processing means 50.

  The tomographic image processing means 50 comprises a computer system such as a personal computer. The tomographic image processing means 50 extracts the interference signals ISa and ISb from the signal photoelectrically converted by the interference light detection means 40, associates the interference signals ISa and ISb with the oscillation frequency of the wavelength sweep light source, and then all have the same frequency. By performing signal connection processing so that the interference signals are spaced apart, one broadband interference signal IS0 is formed. The interference signal IS0 is subjected to frequency analysis including, for example, Fourier transform, thereby obtaining the light reflection intensity at each depth position of the measuring object S.

  Specifically, as shown in FIG. 3, the tomographic image processing means 50 has an IS0 generator 51 that generates an interference signal IS0 from the interference signals ISa and ISb, and frequency analysis of the interference signal IS0, thereby performing analysis at each depth position. A frequency analyzing unit 52 that detects tomographic information r (z) and a tomographic image generating unit 53 that generates a tomographic image using the tomographic information r (z) are provided.

  Here, a method for calculating the tomographic information (reflectance) r (z) based on the interference signal IS0 will be briefly described. For details, see “Mitsuo Takeda,“ Optical Frequency Scanning Spectrum Interference Microscope ”, Optical Technology Contact, 2003, Vol. 41, no. 7, p426-p432 ".

When the measurement light is irradiated to the measurement object S, each optical path when the reflected light and the reference light from the depth of the measurement object S interfere with each other with various optical path length differences (depth positions of the measurement object S). When the light intensity of the interference fringes with respect to the length difference l is S (l), the light intensity I (k) detected by the interference light detection means 40 is
I (k) = ∫ ₀ ^∞ S (l) [1 + cos (kl)] dl (1)
For example, it is represented by a graph as shown in FIG. Here, k is the wave number, and l is the optical path length difference between the reference light and the reflected light. Formula (1) can be considered to be given as an interferogram in the optical frequency domain with the wave number k as a variable. Therefore, the frequency analysis unit 52 can determine the light intensity S (l) of the interference signal IS0 at each wavelength by performing frequency analysis on the spectral interference fringes detected by the interference light detection means by Fourier transform. As shown in FIG. 4, the reflectance at each depth position can be obtained. Then, distance information from the measurement start position of the measuring object S and tomographic information r (z) are acquired. The frequency analysis unit 52 acquires the tomographic information r (z) by using a known spectrum analysis technique such as the maximum entropy method (MEM) or the Yule-Walker method, for example, not limited to the above-described Fourier transform processing. It may be.

  The tomographic image generation unit 53 generates a tomographic image using the tomographic information r (z) detected by the frequency analysis unit 52. Specifically, the measurement lights L1a and L1b are irradiated while scanning in a direction orthogonal to the depth direction z of the measurement target S. Then, the tomographic image generation means 53 acquires tomographic information r (z) for each depth direction at a plurality of measurement points. The tomographic image generation means 53 generates a two-dimensional or three-dimensional tomographic image using a plurality of pieces of tomographic information r (z) acquired at each measurement point.

  Next, an operation example of the optical tomographic imaging apparatus 1 will be described. First, the overall operation will be described first, and the subsequent operation related to the leakage reflected light will be described in detail. Light La swept in the wavelength band Δλa (1295 nm to 1345 nm) is emitted from the light source 10a, and enters the light splitting means 3 through the optical fiber FB1a, the multiplexing means 2 and the optical fiber FB31. In the light splitting means 3, the light La is split into measurement light L1a and reference light L2a, the measurement light L1a is emitted to the optical fiber FB32 side, and the reference light L2a is emitted to the optical fiber FB33 side. The measurement light L1a is guided by the optical fiber FB32, passes through the circulator 4, is guided by the optical fiber FB34, and enters the probe 30 through the optical rotary connector 31.

  On the other hand, light Lb swept in the wavelength band Δλb (1255 nm to 1305 nm) is emitted from the light source 10b and is incident on the light dividing means 3 through the optical fiber FB1b, the multiplexing means 2 and the optical fiber FB31. To do. In the light splitting means 3, the light Lb is split into measurement light L1b and reference light L2b, the measurement light L1b is emitted to the optical fiber FB32 side, and the reference light L2b is emitted to the optical fiber FB33 side. The measurement light L1b is guided by the optical fiber FB32, passes through the circulator 4, is guided by the optical fiber FB34, and enters the probe 30 through the optical rotary connector 31.

  The measurement light L1a and the measurement light L1b are guided by the probe 30 and applied to the measurement object S. Then, the reflected lights L3a and L3b reflected at each depth position z of the measuring object S enter the probe 30, and enter the port b of the circulator 4 along the reverse path to the measuring light. The reflected lights L3a and L3b incident on the port b of the circulator 4 are emitted from the port c to the fiber FB35 and then incident on the wavelength division means 5a.

  In the wavelength division means 5a, most of the reflected light L3a is emitted toward the optical fiber FB36a, and most of the reflected light L3b is emitted toward the optical fiber FB36b. The leakage reflected light L3as, which is a part of the reflected light L3a (a part of the light of 1295 nm to 1310 nm), is emitted to the optical fiber FB36b side, and a part of the reflected light L3b (a part of the light of 1290 nm to 1305 nm). That is, the leakage reflected light L3bs is emitted to the optical fiber FB36a side.

  On the other hand, the reference lights L2a and L2b separated by the light splitting means 3 are guided by the optical fiber FB33, and after the optical path length is changed by the optical path length adjusting means 7 provided in the middle of the optical fiber 33, the wavelength is changed. The light enters the dividing means 5b.

  In the wavelength division means 5b, most of the reference light L2a is emitted to the optical fiber FB37a side, and the leaked reference light L2as is emitted to the optical fiber FB37b side. Further, most of the reference light L2b is emitted toward the optical fiber FB37b, and the leaked reference light L2bs is emitted toward the optical fiber FB37a.

  In the multiplexing / demultiplexing means 6a, the reflected light L3a and the reference light L2a are combined to generate interference light L4a, and this interference light L4a is divided into two and emitted to the interference light detection means 40a. In the multiplexing / demultiplexing means 6b, the reflected light L3b and the reference light L2b are combined to generate interference light L4b, and this interference light L4b is divided into two and emitted to the interference light detection means 40b. In the interference light detection means 40a and 40b, the halved interference light L4a and L4b are each subjected to balance detection using two light detection elements. By this mechanism, the influence of light intensity fluctuation can be suppressed and a clearer image can be obtained.

  The interference light detecting means 40a and 40b respectively photoelectrically convert the interference lights L4a and L4b, detect them as a plurality of interference signals ISa and ISb for the wavelength bands Δλa and Δλb of the light La and Lb, respectively, and the tomographic image processing means 50 Output to.

  The tomographic image processing means 50 generates an interference signal IS0 from the interference signals ISa and ISb, calculates tomographic information r (z) at each depth position from the interference signal IS0, and generates a two-dimensional optical tomographic image. The The generated tomographic image is displayed by a display device 60 such as a CRT (Cathode Ray Tube) or a liquid crystal display device connected to the tomographic image processing means 50.

  Here, with reference to FIG. 6, the operation related to the leaked reflected light will be described. On the left side of FIG. 6 (1), time is plotted on the horizontal axis and wavelength is plotted on the vertical axis, and the state of wavelength sweep of the light La and Lb is shown. FIG. 6 (2) is a diagram showing temporal changes in the light intensities of the light La and Lb emitted from the light sources 10a and 10b, with the horizontal axis representing time and the vertical axis representing light intensity. 6 (3) shows the intensity change of the interference signal output from the interference light detection means 40a, and FIG. 6 (4) shows the intensity change of the interference signal output from the interference light detection means 40b. Corresponding to the time axis of 2), each light is disassembled to help understanding.

  Further, on the right side of FIG. 6 (1), the vertical axis indicates the wavelength, the horizontal axis indicates the branching ratio of the wavelength division means 5a and the wavelength division means 5b, corresponding to the left wavelength axis of FIG. 6 (1), The branching characteristics of the wavelength division means 5a and the wavelength division means 5b are shown. That is, light having a wavelength of 1310 nm or more is emitted to the multiplexing / demultiplexing means 6a side, light having a wavelength of 1290nm or less is emitted to the multiplexing / demultiplexing means 6b side, and light having a wavelength band of 1290nm to 1310nm is multiplexed / demultiplexing means It divides | segments by the division | segmentation rate which changes to about 0-100% to 6a side, and divides | segments to the multiplexing / demultiplexing means 6b side by the division | segmentation rate which changes to about 100-0%.

  As described above, the light source 10a performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλa (1295 nm to 1345 nm). Light La is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. The light source 10b performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλb (1255 nm to 1305 nm). The light Lb is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. Moreover, the sweep of the light Lb in the light source 10b is started 1 ms later than the sweep of the light La in the light source 10a.

  Since the sweep wavelength band of the light La is λa (1295 nm to 1345 nm) and the sweep wavelength band of the light Lb is λb (1255 nm to 1305 nm), most of the reflected light L3a is multiplexed / demultiplexed in the wavelength division means 5a. The light is emitted toward the means 6a, and most of the reflected light L3b is emitted toward the multiplexing / demultiplexing means 6b. On the other hand, a part of the reflected light L3a leaks to the multiplexing / demultiplexing means 6b side to become a leakage reflected light L3as, and a part of the reflected light L3b leaks to the multiplexing / demultiplexing means 6a side to become a leakage reflected light L3bs. .

  In the wavelength division means 5b, most of the reference light L2a is emitted toward the multiplexing / demultiplexing means 6a, and most of the reference light L2b is emitted toward the multiplexing / demultiplexing means 6b. On the other hand, a part of the reference light L2a leaks to the multiplexing / demultiplexing means 6b side to become a leaked reference light L2as, and a part of the reference light L2b leaks to the multiplexing / demultiplexing means 6a side to become a leaked reference light L2bs. .

  For this reason, in the multiplexing / demultiplexing means 6a, simultaneously with the interference light L4a by the reflected light L3a and the reference light L2a, the leakage interference light L4bs by the leakage reflected light L3bs and the leakage reference light L2bs is generated. Similarly, in the multiplexing / demultiplexing means 6b, simultaneously with the interference light L4b due to the reflected light L3b and the reference light L2b, the leakage interference light L4as due to the leakage reflected light L3as and the leakage reference light L2as is generated.

  That is, the interference light L4a and the leakage interference light L4bs are incident on the interference light detection means 40a, and the interference light L4b and the leakage interference light L4as are incident on the interference light detection means 40b. On the other hand, since the light La and the light Lb are swept at the timing shown in FIG. 6A, the interference light detection unit 40a has a leakage interference with the interference light L4a as shown in FIG. 6C. The light L4bs is incident at a different timing. In addition, as shown in FIG. 6 (4), the interference light L4b and the leakage interference light L4as are incident on the interference light detection means 40b at different timings.

  In addition, the tomographic image processing means 50 synchronizes with the trigger for starting the wavelength sweep of the light sources 10a and 10b, respectively, and the output of the interference light detection means 40a is detected during 2.5 ms after the start of the sweep of the light source 10a. The value is recognized as the interference signal ISa, and the output of the interference light detection means 40b recognizes the detection value detected during 2.5 ms after the start of the sweep of the light source 10b as the interference signal ISb. Thereby, the tomographic image processing means 50 can accurately recognize the interference signals ISa and ISb.

  As is clear from the above description, in the present embodiment, the light source 10a emits light in a wavelength band (1290 nm to 1310 nm) in which light is divided in two directions by the wavelength division means 5a and the wavelength division means 5b. During this period, light is emitted only from the light source 10a, and while light in this wavelength band (1290 nm to 1310 nm) is emitted from the light source 10b, light is emitted only from the light source 10b. While the means 40a is detecting the interference light L4a, the leakage interference light L4bs is detected by the interference light detection means 40a, or while the interference light detection means 40b is detecting the interference light L4b, the leakage interference The light L4as is not detected by the interference light detection main means 40b. For this reason, the interference light L4a and the interference light L4b can be accurately detected. Further, while light having a wavelength of 1310 nm or more is emitted from the light source 10a and light having a wavelength of 1290 nm or less is emitted from the light source 10b, the light emitted from each light source is wavelength-reduced by the wavelength dividing means 5a and the wavelength dividing means 5b. Since the interference light is divided and detected by the interference light detection means 40a and 40b, even if a plurality of lights having different wavelengths are irradiated onto the measuring object S at the same time, a plurality of interferences caused by the plurality of interference lights generated at this time Since the signals are not mixed and a plurality of interference signals can be obtained simultaneously for each light, the measurement rate can be improved as compared with the conventional case. For this reason, it is possible to detect interference signals over a wide band and continuous spectrum, and to acquire a high-resolution tomographic image at high speed.

  Furthermore, in the conventional apparatus including a plurality of light sources and a plurality of gain media, it is necessary to perform control in synchronization so that the wavelength of light incident on the interference light detection unit becomes one. According to the optical tomographic imaging apparatus, such control is unnecessary, and the apparatus can be simplified. Further, in the optical tomographic imaging apparatus of the present invention, each interference light detection means can be optimized according to the wavelength band of each light, so that the detection accuracy in each interference light detection means is improved and acquired. The resolution of the tomographic image can be improved. Furthermore, the components used for the interference light detection means do not need to support broadband light, and only need to support the wavelength band of each light. Can be used, and the device configuration becomes easy.

  In addition, since the wavelength band Δλa (1295 nm to 1345 nm) of the laser light La emitted from the light source 10a and a part of the wavelength band Δλb (1255 nm to 1305 nm) of the laser light Lb emitted from the light source 10b overlap, By connecting the interference signal ISa and the interference signal ISb to form one interference signal IS0, a tomographic image can be generated based on the interference signal IS0, and a higher-resolution tomographic image can be acquired.

  Next, an optical tomographic imaging apparatus 200 according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a schematic configuration diagram of the optical tomographic imaging apparatus 200. The optical tomographic imaging apparatus 200 is different from the optical tomographic imaging apparatus 100 in FIG. 1 in the configuration of the light source unit 20 and the configuration of the interference light detection means 41a and 41b. In the following, this difference will be mainly described, and in the optical tomographic imaging apparatus 200 of FIG. 7, the same components as those of the optical tomographic imaging apparatus 100 of FIG.

  A state of wavelength sweeping of the light sources 20a and 20b of the light source unit 20 is shown in FIG. The light source 20a has wavelength selection means 21a, and performs wavelength sweeping at intervals of 5 ms within a wavelength band Δλa (1295 nm to 1365 nm). The light La is emitted for 3.5 ms, and no light is emitted for the remaining 1.5 ms. The light source 10b has wavelength selection means 21b, and performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλb (1235 nm to 1305 nm). The light Lb is emitted for 3.5 ms, and no light is emitted for the remaining 1.5 ms. Moreover, the sweep of the light La in the light source 10a and the sweep of the light Lb in the light source 10b are started simultaneously.

  The interference light detecting means 41a synchronizes with the trigger for starting the wavelength sweep, outputs only the detection result from the start of the sweep to 2.75 ms to the tomographic image processing means 50, and discards the detection results at other times. . The interference light detection means 41b synchronizes with the trigger for starting the wavelength sweep, and outputs only the detection result from 0.75 ms to 3.5 ms after the sweep start to the tomographic image processing means 50. The detection result is discarded. FIG. 8 (2) is a diagram showing temporal changes in the light intensities of the light La and Lb emitted from the light sources 20a and 20b. The horizontal axis represents time and the vertical axis represents light intensity. FIG. 8 (3) shows the intensity change of the interference signal output from the interference light detection means 41a, and FIG. 8 (4) shows the intensity change of the interference signal output from the interference light detection means 41b. Corresponding to the time axis of 2), each light is disassembled to help understanding.

  Similar to the optical tomographic imaging apparatus 100 shown in FIG. 1, during the period from 2.75 ms to 3.5 ms after the start of sweeping, in addition to the interference light L4a, the leakage interference light L4bs is also incident on the interference light detection means 41a. (See FIG. 6 (3)), but the output during this time is discarded. Further, during the period from the start of the sweep to 0.75 ms, the interference light detection means 41b is also incident with the leakage interference light L4as in addition to the interference light L4b (see FIG. 6 (4)), but the output during this time is also output. Discarded. That is, while light from the light source 20a is emitted in a wavelength band (1290 nm to 1310 nm) in which light is divided in two directions in the wavelength division unit 5a and the wavelength division unit 5b, the detection result of the interference light detection unit 41b is While being discarded and the light of this wavelength band (1290 nm to 1310 nm) is emitted from the light source 20b, the detection result of the interference light detection means 41a is discarded.

  The tomographic image processing means 50 recognizes the signal input from the interference light detection means 40a as the interference signal ISa, recognizes the signal input from the interference light detection means 40b as the interference signal ISb, and generates a tomographic image.

  That is, the interference light detection means 41a and 41b emit light from one of the light sources 20a or 20b in a wavelength band (1290 nm to 1310 nm) in which light is divided in two directions in the wavelength division means 5a and the wavelength division means 5b. While detecting the interference light L4a and the interference light L4b, the interference light L4a and the interference light L4b can be accurately detected without detecting the leakage interference light by detecting only the interference signal based on the light emitted from the one light source. Can do.

  Next, an optical tomographic imaging apparatus 250 according to the third embodiment of the present invention will be described with reference to FIGS. The optical tomographic imaging apparatus 250 is different from the optical tomographic imaging apparatus 200 of FIG. 7 in that the configurations of the interference light detection means 40a and 40b and the tomographic image processing means 55 are different. The number is attached | subjected and the schematic block diagram is shown. In the following, this difference will be mainly described, and in the optical tomographic imaging apparatus 250, the description of the same configuration as that of the optical tomographic imaging apparatus 200 will be omitted.

  The interference light detection means 40a and the interference light detection means 40b have the same configuration as that used in the optical tomographic imaging apparatus 1 shown in FIG.

  The tomographic image processing means 55 synchronizes with the trigger of the wavelength sweep start, and the output of the interference light detection means 40a recognizes only the detection result from the start of the sweep to 2.75 ms as the interference signal ISa, and the interference The output of the light detection means 40b recognizes only the detection result between 0.75 ms and 3.5 ms after the start of the sweep as the interference signal ISb, and generates a tomographic image.

  FIG. 9 (1) is a diagram showing the temporal change in the light intensity of the light La and Lb emitted from the light sources 20a and 20b, with the horizontal axis representing time and the vertical axis representing light intensity. FIG. 9 (2) shows the intensity change of the interference signal output from the interference light detection means 40a, and FIG. 9 (3) shows the intensity change of the interference signal output from the interference light detection means 40b. Corresponding to the time axis of 2), each light is disassembled to help understanding.

  As can be seen from FIG. 9, during the period from 2.75 ms to 3.5 ms after the start of the sweep, in addition to the interference light L4a, the leakage interference light L4bs is also incident on the interference light detection means 40a. Further, during the period from the start of sweeping to 0.75 ms, leaked interference light L4as is also incident on the interference light detection means 40b in addition to the interference light L4b. However, the signal during this period is not recognized as an interference signal by the tomographic image processing means 55. That is, the tomographic image processing unit 55 is configured to emit light from the light source 20a while the light in the wavelength band (1290 nm to 1310 nm) in which light is divided in two directions by the wavelength dividing unit 5a and the wavelength dividing unit 5b is emitted. Only the interference signal based on the light emitted from the light source is recognized as an interference signal, and the light emitted from the light source 20b is emitted while light in this wavelength band (1290 nm to 1310 nm) is emitted from the light source 20b. Only the based interference signal is recognized as an interference signal.

  That is, while the tomographic image processing means emits light in a wavelength band (1290 nm to 1310 nm) in which light is divided in two directions in the wavelength division means 5a and the wavelength division means 5b from one of the light sources 20a or 20b. By using only the interference signal based on the light emitted from one of the light sources, the interference signals ISa and ISb can be accurately recognized without being affected by the leakage interference light.

  Next, an optical tomographic imaging apparatus 300 according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a schematic configuration diagram of the optical tomographic imaging apparatus 300. The optical tomographic imaging apparatus 300 is an SS-OCT apparatus using a Mach-Zehnder interferometer. However, in comparison with the optical tomographic imaging apparatus 100 of FIG. 1, instead of the optical splitting means 3 and the wavelength splitting means 5a and 5b, The light splitting means 3a and 3b and the wavelength splitting means 5 are basically different. In the following, this difference will be mainly described. In the optical tomographic imaging apparatus 300 of FIG. 10, the same components as those of the optical tomographic imaging apparatus 100 of FIG.

  The optical tomographic imaging apparatus 300 includes a light source 10a that emits a laser beam La whose wavelength is repeatedly swept within a wavelength band Δλa (1000 nm to 1100 nm), and a wavelength that is repeatedly swept within a wavelength band Δλb (900 nm to 1020 nm). A light source unit 10 having a light source 10b that emits laser light Lb, and light splitting means for splitting light La and Lb emitted from the light source unit 10 into measurement light L1a and reference light L2a, measurement light L1b, and reference light L2b, respectively. 3a, 3b, the measurement light L1a, and the measurement light L1b are combined, and the reflected light from the measurement target S when the measurement light L1a, L1b is irradiated onto the measurement target S is wavelength-divided into reflected light L3a and L3b Wavelength dividing means 5 for combining, reflected light L3a, L3b and combining light 6a, 6b for combining the reference light L2a, L2b, and reflected light L3a and reference light L2a by the combining means 6a. The interference light L4a generated when the light is waved is used as an interference signal ISa, and the interference light L4b generated when the reflected light L3b and the reference light L2b are combined by the combining means 6b is detected as the interference signal ISb for each light. A plurality of interference light detection means 40a, 40b, and a tomographic image processing means 50 for acquiring a tomographic image of the measuring object S using the interference signals ISa, ISb detected by the interference light detection means 40a, 40b.

  Note that the measurement light L1a, the reference light L2a, the reflected light L3a, and the interference light L4a are based on the light La and are light in the same wavelength band as the light La. Further, the measurement light L1b, the reference light L2b, the reflected light L3b, and the interference light L4b are based on the light Lb and are light in the same wavelength band as the light Lb.

  The light source 10a of the light source unit 10 emits a laser beam La whose wavelength is repeatedly swept within the wavelength band Δλa (1000 nm to 1100 nm), and the light source 10b repeatedly sweeps the wavelength within the wavelength band Δλb (900 nm to 1020 nm). Laser beam Lb is emitted. The semiconductor optical amplifiers 11a and 11b are composed of InGaAs / AlGaAs elements having a light emission band at a wavelength of 900 nm to 1100 nm, for example. The light source 10a performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλa (1000 nm to 1100 nm). The light La is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. The light source 10b performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλb (900 nm to 1020 nm). The light Lb is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. Moreover, the sweep of the light Lb in the light source 10b is started 1 ms later than the sweep of the light La in the light source 10a.

  The light splitting means 3a and 3b are composed of, for example, a 2 × 2 optical coupler having a branching ratio of 90:10. The light splitting means 3a splits the light La into measurement light L1a and reference light L2a, and the light splitting means 3b splits the light Lb into measurement light L1b and reference light L2b. At this time, the light dividing means 3a and 3b divide at a ratio of measurement light: reference light = 90: 10.

  A wavelength dividing means 5 is provided on the optical path between the light dividing means 3 a and the probe 30 and on the optical path between the light dividing means 3 b and the probe 30.

  The wavelength division means 5 has a function of wavelength dividing light according to a set wavelength, and is constituted by, for example, a WDM (Wavelength Division Multiplexing) coupler. The wavelength division means 5 combines the measurement lights L1a and L1b incident from the light division means 3a and 3b, respectively, and emits them to the probe 30 side. Of the light incident from the probe 30 side, light having a wavelength of 1020 nm or more is emitted to the circulator 4a side, and light having a wavelength of 1000 nm or less is emitted to the circulator 4b side. Furthermore, light having a wavelength band of 1000 nm to 1020 nm is emitted in both directions. Specifically, light with a wavelength band of 1000 nm to 1020 nm is divided into a circulator 4a side at a division ratio that changes from about 0 to 100%, and the circulator 4b side is divided at a division ratio that changes from about 100 to 0%. To do. For this reason, most of the reflected light L3a is emitted toward the circulator 4a, and most of the reflected light L3b is emitted toward the circulator 4b. On the other hand, a part of the reflected light L3a (a part of light having a wavelength of 1000 nm to 1020 nm) is emitted to the circulator 4a side to become a leaked reflected light L3as. Further, a part of the reflected light L3b (a part of light having a wavelength of 1000 nm to 1020 nm) is emitted to the circulator 4b side to become a leakage reflected light L3bs.

  The reflected light L3a is combined with the reference light L2a in the combining means 6a, and the reflected light L3b is combined with the reference light L2b in the combining means 6b. A transmission type optical path length adjusting means 7a is provided in the optical path of the reference light L2a from the light splitting means 3a to the multiplexing means 6a, and the optical path of the reference light L2b from the light splitting means 3b to the multiplexing means 6b is provided in the optical path. A transmissive optical path length adjusting means 7b is provided. The optical path length adjusting means 7a and 7b change the optical path lengths of the reference lights L2a and L2b, respectively, in order to adjust the position where the tomographic image acquisition is started.

  The interference light detection means 40a and 40b have a function of photoelectrically converting the interference lights L4a and L4b, respectively, and detecting them as a plurality of interference signals ISa and ISb for the wavelength bands Δλa and Δλb of the lights La and Lb, respectively. . The interference light detection means 40a is formed of an Si element, and the interference light detection means 40b is formed of an InGaAs element.

  Next, an operation example of the optical tomographic imaging apparatus 300 will be described. Light La swept in the wavelength band Δλa (1000 nm to 1100 nm) is emitted from the light source 10a, guided by the optical fiber FB1a, and incident on the light splitting means 3a. In the light dividing means 3a, the light La is divided into the measuring light L1a and the reference light L2a, the measuring light L1a is emitted to the optical fiber FB2a side, and the reference light L2a is emitted to the optical fiber FB3a side. The measurement light L1a is guided by the optical fiber FB2a, passes through the circulator 4a, is guided by the optical fiber FB4a, and enters the wavelength division means 5.

  On the other hand, from the light source 10b, the light Lb swept in the wavelength band Δλb (900 nm to 1020 nm) is emitted, guided by the optical fiber FB1b, and incident on the light dividing means 3b. In the light splitting means 3b, the light Lb is split into measurement light L1b and reference light L2b, the measurement light L1b is emitted to the optical fiber FB2b side, and the reference light L2b is emitted to the optical fiber FB3b side. The measurement light L1b is guided by the optical fiber FB2b, passes through the circulator 4b, is guided by the optical fiber FB4b, and enters the wavelength division means 5.

  In the wavelength division means 5, the measurement light L1a and the measurement light L1b are combined, guided by the optical fiber FB5, incident on the probe 30 via the optical rotary connector 31, and guided by the probe 30 to be measured S. Is irradiated. Then, the reflected lights L3a and L3b reflected at the respective depth positions z of the measuring object S enter the probe 30, and enter the wavelength dividing means 5 along a path opposite to the measuring light.

  In the wavelength division means 5, most of the reflected light L3a is emitted toward the circulator 4a, and most of the reflected light L3b is emitted toward the circulator 4b.

  The reflected light L3a guided by the optical fiber FB4a passes through the circulator 4a, is guided by the optical fiber FB6a, and enters the multiplexing means 6a. On the other hand, the reference light L2a divided by the light dividing means 3a is incident on the multiplexing means 6a after the optical path length is changed by the optical path length adjusting means 7a provided in the middle of the optical fiber FB3a.

  In the multiplexing means 6a, the reflected light L3a and the reference light L2a are multiplexed, and the interference light L4a generated by this multiplexing is bisected and emitted to the interference light detection means 40a. In the interference light detection means 40a, the interference light L4a is balance-detected and photoelectrically converted, and an interference signal ISa is generated and output to the tomographic image processing means 50.

  Similarly, the reflected light L3b guided by the optical fiber FB4b passes through the circulator 4b, is guided by the optical fiber FB6b, and enters the multiplexing means 6b. On the other hand, the reference light L2b split by the light splitting means 3b is incident on the multiplexing means 6b after the optical path length is changed by the optical path length adjusting means 7b provided in the middle of the optical fiber FB3b.

  In the multiplexing means 6b, the reflected light L3b and the reference light L2b are multiplexed, and the interference light L4b generated by this multiplexing is bisected and emitted to the interference light detection means 40b. In the interference light detection means 40b, the interference light L4b is balance-detected and photoelectrically converted to generate an interference signal ISb, which is output to the tomographic image processing means 50. Since the configuration and operation of the tomographic image processing means 50 are the same as those in the first embodiment, a duplicate description is omitted.

  Hereinafter, an operation related to the leaked reflected light will be described. As described above, the light source 10a performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλa (1000 nm to 1100 nm). The light La is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. The light source 10b performs wavelength sweeping at intervals of 5 ms within the wavelength band Δλb (900 nm to 1020 nm). The light Lb is emitted for 2.5 ms, and no light is emitted for the remaining 2.5 ms. Moreover, the sweep of the light Lb in the light source 10b is started 1 ms later than the sweep of the light La in the light source 10a.

  Since the sweep wavelength band of the light La is λa (1000 nm to 1100 nm) and the sweep wavelength band of the light Lb is λb (900 nm to 1020 nm), most of the reflected light L3a is on the circulator 4a side in the wavelength division means 5. And most of the reflected light L3b is emitted toward the circulator 4b. On the other hand, a part of the reflected light L3a (a part of light of 1000 nm to 1020 nm) leaks to the circulator 4b side to become a leaked reflected light L3as, and a part of the reflected light L3b (a part of light of 1000 nm to 1020 nm) It leaks to the circulator 4a side and becomes leaked reflected light L3bs. That is, the interference light L4a and the leakage reflected light L3bs are incident on the interference light detection means 40a, and the interference light L4b and the leakage reflection light L3as are incident on the interference light detection means 40b. On the other hand, since the scanning of the light Lab is started with a delay of 1 ms from the light La, the leakage reflected light L3bs is detected by the interference light detection main means 40a while the interference light detection means 40a is detecting the interference light L4a. There is nothing. Further, while the interference light detection means 40b is detecting the interference light L4b, the leakage reflected light L3as is not detected by the interference light detection main means 40b. For this reason, the interference light L4a and the interference light L4b can be accurately detected.

  Next, an optical tomographic imaging apparatus 400 according to a fifth embodiment of the present invention will be described with reference to FIG. 11 and FIG. FIG. 11 is a schematic configuration diagram of the optical tomographic imaging apparatus 400. The optical tomographic imaging apparatus 400 is an SS-OCT apparatus using a Fizeau interferometer, and is characterized in that a probe 430 different from the probe 30 of the optical tomographic imaging apparatus 100 of FIG. 1 is used. In the following, this feature will be mainly described, and in the optical tomographic imaging apparatus 400 of FIG.

  As shown in FIG. 12, the probe 430 is provided with a light splitting means 431 at the exit end on the measurement object S side, transmits a part of the light from the light source unit 10 to be used as measurement light, and the rest. Is configured to reflect a part of the light as reference light. In the example shown in FIG. 12, a half mirror is used as the light splitting means 431. However, instead of the half mirror, a reflection film that reflects a part of incident light may be provided on the exit end face of the probe 430. Alternatively, a film is not formed on the exit end face of the probe 430, and the exit end face is set as a plane orthogonal to the optical axis of the incident light, and this plane is optically polished to form an optical flat surface. You may make it use the light reflected by (For example, the refractive index difference of glass and air) as reference light.

  In the optical tomographic imaging apparatus 400, the light La emitted from the light source 10a and guided by the optical fiber FB1a passes through the circulator 4a, is guided by the optical fiber FB4a, and enters the wavelength dividing means 5. Similarly, the light Lb emitted from the light source 10b and guided by the optical fiber FB1b passes through the circulator 4b, is guided by the optical fiber FB4b, and enters the wavelength dividing means 5.

  The light La and the light Lb are combined in the wavelength division means 5, guided by the optical fiber FB 5, and incident on the probe 430 through the optical rotary connector 31. In the light splitting means 431 at the emission end of the probe 430, part of the light La and Lb is transmitted to become measurement light L1a and L1b, and the remaining part is reflected to become reference light L2a and L2b. The measurement lights L1a and L1b are applied to the measurement object S, and the reflected lights L3a and L3b at this time are guided by the probe 430 and the optical fiber FB5 and enter the wavelength division means 5. Further, the reference lights L2a and L2b reflected by the light dividing means 431 are also guided by the probe 430 and the optical fiber FB5 and enter the wavelength dividing means 5.

  The reflected lights L3a and L3b and the reference lights L2a and L2b incident on the wavelength dividing means 5 are divided according to the wavelength band, the reflected light L3a and the reference light L2a are emitted to the optical fiber FB4a side, and the reflected light L3b and the reference light L2b. Is emitted to the optical fiber FB4b side.

  Thereafter, the reflected light L3a and the reference light L2a are guided by the optical fiber FB41a via the circulator 4a and enter the light splitting means 401a. The light splitting means 401a is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 50:50. About 50% of the reflected light L3a and reference light L2a of the light incident on the light splitting means 401a are emitted toward the optical fiber FB42a, guided as they are, and incident on the multiplexing means 4a. The remaining 50% of the reflected light L3a and the reference light L2a that are incident on the light splitting means 401a are emitted to the optical fiber FB43a side, and the optical path length is changed by the optical path length adjusting means 7a provided in the middle path. After receiving, the light enters the multiplexing means 4a.

  In the multiplexing means 4a, interference between the reference light L2a guided by the optical fiber FB42a and the reflected light L3a guided by the optical fiber FB43a, or by the reflected light L3a guided by the optical fiber FB42a and the optical fiber FB43a. Interference light L4a is generated by interference with the guided reference light L2a. The interference light L4a is divided into two and emitted to the interference light detection means 40a.

  The same applies to the reflected light L3b and the reference light L2b emitted to the optical fiber FB4b side, and these lights are guided by the optical fiber FB41b via the circulator 4b and enter the light splitting means 401b. . The light splitting means 401b is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 50:50. About 50% of the reflected light L3b and reference light L2b of the light incident on the light splitting means 401b are emitted to the optical fiber FB42b side, guided as they are, and incident on the multiplexing means 4b. The remaining 50% of the reflected light L3b and the reference light L2b of the light incident on the light splitting means 401b are emitted to the optical fiber FB43b side, and the optical path length is changed by the optical path length adjusting means 7b provided in the middle path. After receiving, the light enters the multiplexing means 4b.

  In the multiplexing means 4b, interference between the reference light L2b guided by the optical fiber FB42b and the reflected light L3b guided by the optical fiber FB43b, or by the reflected light L3b guided by the optical fiber FB42b and the optical fiber FB43b. Interference light L4b is generated by interference with the guided reference light L2b. The interference light L4b is divided into two and emitted to the interference light detection means 40b.

  The subsequent configuration and operation of the interference light detection units 40a and 40b and the tomographic image processing unit 50 are the same as those in the first embodiment, and thus a duplicate description is omitted.

  Next, an optical tomographic imaging apparatus 500 according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 13 is a schematic configuration diagram of the optical tomographic imaging apparatus 500. The optical tomographic imaging apparatus 500 is an SS-OCT apparatus using a Fizeau interferometer. However, compared with the optical tomographic imaging apparatus 400 of FIG. The difference is that the dividing means 505 is provided. In the following, this difference will be mainly described, and in the optical tomographic imaging apparatus 500 of FIG. 13, the same components as those of the optical tomographic imaging apparatus of the above-described embodiment are denoted by the same reference numerals and redundant description will be omitted. .

  In the optical tomographic imaging apparatus 500, the light La emitted from the light source 10a and guided by the optical fiber FB1a and the light Lb emitted from the light source 10b and guided by the optical fiber FB1b are transmitted to the combining unit 308. Incident and combined. The combined light La and Lb is guided by the optical fiber FB31, passes through the circulator 501, is guided by the optical fiber FB51, and enters the probe 430 through the optical rotary connector 31. In the light splitting means 431 at the emission end of the probe 430, the light La and Lb are split into measurement light L1a and L1b and reference light L2a and L2b. The measurement lights L1a and L1b are applied to the measurement object S, and at this time, reflected lights L3a and L3b are generated. The reflected lights L3a and L3b and the reference lights L2a and L2b are guided by the probe 430 and the optical fiber FB51, enter the wavelength division unit 505 via the circulator 501.

  The wavelength division means 505 has the same wavelength division function as the wavelength division means 5 in the optical tomographic imaging apparatus 300 shown in FIG. 10, and is constituted by, for example, a WDM coupler. Of the light incident on the wavelength division means 505, most of the reflected light L3a and the reference light L2a are emitted to the optical fiber FB41a side, and most of the reflected light L3b and the reference light L2b are emitted to the optical fiber FB41b side. The optical fiber FB41a is coupled to the light splitting means 401a, and the optical fiber FB41b is coupled to the light splitting means 401b. Since the operations after the light splitting means 401a and 401b are the same as those in the fourth embodiment, the description thereof is omitted.

  In the optical tomographic imaging apparatus 500 described above, an interferometer is disposed downstream of the wavelength dividing unit 505 to divide the light for each wavelength band, and then interfere with each other. Later, light may be divided for each wavelength band and guided to the interference light detecting means.

  Next, an optical tomographic imaging apparatus 600 according to the seventh embodiment of the present invention will be described with reference to FIG. FIG. 14 is a schematic configuration diagram of the optical tomographic imaging apparatus 600. The optical tomographic imaging apparatus 600 is an SS-OCT apparatus using a Michelson interferometer. In the optical tomographic imaging apparatus 600 of FIG. 14, the same components as those of the optical tomographic imaging apparatus of the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the optical tomographic imaging apparatus 600, the light La emitted from the light source 10a and guided by the optical fiber FB1a passes through the circulator 4a, is guided by the optical fiber FB61a, and enters the light splitting means 603a. The light dividing means 603a is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 90:10. Note that the light splitting means 603a in this embodiment also functions as a multiplexing means. The light splitting means 603a splits the light La into measurement light L1a and reference light L2a so that the ratio of measurement light: reference light = 90: 10, emits the measurement light L1a to the optical fiber FB4a side, and the reference light L2a is emitted to the optical fiber FB62a side. The measurement light L1a guided by the optical fiber FB4a is incident on the wavelength dividing means 5.

  Further, the light Lb emitted from the light source 10b and guided by the optical fiber FB1b passes through the circulator 4b, is guided by the optical fiber FB61b, and enters the light splitting means 603b. The light dividing means 603b is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 90:10. Note that the light splitting means 603b in this embodiment also functions as a multiplexing means. The light splitting means 603b splits the light Lb into the measurement light L1b and the reference light L2b so that the ratio of measurement light: reference light = 90: 10, and emits the measurement light L1b to the optical fiber FB4b side. L2b is emitted to the optical fiber FB62b side. The measurement light L1b guided by the optical fiber FB4b is incident on the wavelength dividing means 5.

  In the wavelength division means 5, the measurement light L1a and the measurement light L1b are combined, guided by the optical fiber FB5, incident on the probe 30 via the optical rotary connector 31, and guided by the probe 30 to the measurement object S. Irradiated. The reflected lights L3a and L3b at this time are incident on the probe 30, and enter the wavelength dividing means 5 along a path opposite to that of the measurement light. In the wavelength division means 5, the reflected light L3a and the reflected light L3b are divided, the reflected light L3a is emitted to the optical fiber FB4a side and incident on the light dividing means 603a, and the reflected light L3b is emitted to the optical fiber FB4b side and light. The light enters the dividing means 603b.

  On the other hand, the reference light L2a is subjected to the change of the optical path length by the reflection type optical path length adjusting means 620a connected to the end of the optical fiber FB62a, and then is guided again by the optical fiber FB62a and enters the light splitting means 603a. . Further, the reference light L2b is also subjected to the change of the optical path length by the reflection type optical path length adjusting means 620b connected to the end of the optical fiber FB62b, and then is guided again by the optical fiber FB62b and enters the light splitting means 603b. .

  In the light splitting means 603a, the reflected light L3a and the reference light L2a are combined to generate the interference light L4a. The interference light L4a is guided by the optical fiber FB61a and passes through the circulator 4a by the optical fiber FB63a. It is guided and enters the light splitting means 605a. The light splitting means 605a is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 50:50. In the light splitting means 605a, the interference light L4a is divided into two and emitted to the interference light detection means 40a.

  Similarly, in the light splitting means 603b, the reflected light L3b and the reference light L2b are combined to generate the interference light L4b. The interference light L4b is guided by the optical fiber FB61b and passes through the circulator 4b. It is guided by the fiber FB63b and enters the light splitting means 605b. The light splitting means 605b is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 50:50. In the light splitting means 605b, the interference light L4b is divided into two and emitted to the interference light detection means 40b.

  The subsequent configuration and operation of the interference light detection units 40a and 40b and the tomographic image processing unit 50 are the same as those in the first embodiment, and thus a duplicate description is omitted.

  Next, an optical tomographic imaging apparatus 700 according to an eighth embodiment of the present invention will be described with reference to FIG. FIG. 15 is a schematic configuration diagram of the optical tomographic imaging apparatus 700. The optical tomographic imaging apparatus 700 is an SS-OCT apparatus using a Michelson interferometer. However, as compared with the optical tomographic imaging apparatus 600 of FIG. The difference is that the dividing means 705 is provided. In the following, this difference will be mainly described. In the optical tomographic imaging apparatus 700 of FIG. 14, the same components as those of the optical tomographic imaging apparatus of the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted. .

  In the optical tomographic imaging apparatus 700, the light La emitted from the light source 10a and guided by the optical fiber FB1a and the light Lb emitted from the light source 10b and guided by the optical fiber FB1b are transmitted to the wavelength dividing unit 5. Incident and combined. The combined light La and Lb is guided by the optical fiber FB31, passes through the circulator 501, is guided by the optical fiber FB71, and enters the light splitting means 703.

  The light dividing means 703 is composed of, for example, a 2 × 2 optical coupler having a branching ratio of 90:10. Note that the light splitting means 703 in this embodiment also functions as a multiplexing means. The light splitting means 703 splits the light La and Lb into measurement light L1a and L1b and reference light L2a and L2b so that the ratio of measurement light: reference light = 90: 10, and the measurement light L1a and L1b is an optical fiber. The light is emitted to the FB 72 side, and the reference lights L2a and L2b are emitted to the optical fiber FB73 side.

  The measurement lights L1a and L1b are incident on the probe 30 via the optical rotary connector 31, guided by the probe 30, and irradiated onto the measurement object S. The reflected lights L3a and L3b at this time are incident on the probe 30, guided to the probe 30 and the optical fiber FB72, and incident on the light splitting means 703.

  On the other hand, the reference beams L2a and L2b are subjected to the change of the optical path length by the reflection type optical path length adjusting unit 720 connected to the end of the optical fiber FB73, and then guided again by the optical fiber FB73 to the light splitting unit 703. Incident.

  In the light splitting means 703, the reflected lights L3a and L3b and the reference lights L2a and L2b are combined. The interference light L4a is generated by combining the reflected light L3a and the reference light L2a, and the interference light L4b is generated by combining the reflected light L3b and the reference light L2b. At this time, since the light La and Lb are emitted from different light sources, interference light is not generated by the combination of the reflected light L3a and the reference light L2b and the combination of the reflected light L3b and the reference light L2a.

  The interference lights L4a and L4b are guided by the optical fiber FB71, are guided by the optical fiber FB74 via the circulator 501, and are incident on the wavelength division means 705.

  The wavelength division means 705 has the wavelength division function of the wavelength division means 5 in the optical tomographic imaging apparatus 1 shown in FIG. 1, and is composed of, for example, a WDM coupler. In the wavelength division means 705, most of the interference light L4a is emitted toward the optical fiber FB75a and enters the light division means 701a, and most of the interference light L4b is emitted toward the optical fiber FB75b and enters the light division means 701b. To do. The light splitting means 701a and 701b are composed of 2 × 2 optical couplers having a branching ratio of 50:50, for example. In the light splitting means 701a and 701b, the interference lights L4a and L4b are respectively divided into two and emitted to the interference light detection means 40a and 40b. The wavelength dividing means functions as the wavelength dividing means of the present invention.

  The subsequent configuration and operation of the interference light detection units 40a and 40b and the tomographic image processing unit 50 are the same as those in the first embodiment, and thus a duplicate description is omitted.

  Next, an optical tomographic imaging apparatus 800 according to the ninth embodiment of the present invention will be described with reference to FIG. FIG. 16 is a schematic configuration diagram of an optical tomographic imaging apparatus 800. The optical tomographic imaging apparatus 800 is an SS-OCT apparatus using a Michelson interferometer. In the optical tomographic imaging apparatus 800 of FIG. 16, the same components as those of the optical tomographic imaging apparatus of the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The optical tomographic imaging apparatus 800 uses a light dividing means 803 instead of the light dividing means 703 of the optical tomographic imaging apparatus 700. The light splitting means 803 is composed of, for example, a 2 × 2 optical coupler with a branching ratio of 50:50. The process is the same as that of the optical tomographic imaging apparatus 700 until the light La and Lb emitted from the light sources 10a and 10b are multiplexed by the multiplexing unit 2 and guided by the optical fiber FB71 after passing through the circulator 501.

  Thereafter, the lights La and Lb enter the light splitting means 803, and are split into the measuring lights L1a and L1b and the reference lights L2a and L2b so that the ratio of measuring light: reference light = 50: 50 is obtained in the light splitting means 803. The measurement lights L1a and L1b are emitted to the optical fiber FB72 side, and the reference lights L2a and L2b are emitted to the optical fiber FB73 side.

  The measurement lights L1a and L1b are incident on the probe 30 via the optical rotary connector 31, guided by the probe 30, and irradiated onto the measurement object S. The reflected lights L3a and L3b at this time enter the probe 30, are guided by the probe 30 and the optical fiber FB72, and enter the light splitting means 803.

  On the other hand, the reference beams L2a and L2b are subjected to the change of the optical path length by the reflection type optical path length adjusting unit 720 connected to the end of the optical fiber FB73, and then are guided again by the optical fiber FB73 to the light splitting unit 803. Incident.

  In the light splitting means 803, the reflected lights L3a and L3b and the reference lights L2a and L2b are combined. The interference light L4a is generated by combining the reflected light L3a and the reference light L2a, and the interference light L4b is generated by combining the reflected light L3b and the reference light L2b. About 50% of the interference lights L4a and L4b are emitted to the optical fiber FB81 side and enter the wavelength division unit 806. The remaining 50% of the interference lights L4a and L4b are emitted to the optical fiber FB71 side, guided by the optical fiber 82 via the circulator 501, and enter the wavelength dividing means 807.

  The wavelength division means 806 and 807 have the wavelength division function of the wavelength division means 5 in the optical tomographic imaging apparatus 300 shown in FIG. 9, and are composed of, for example, a WDM coupler. The wavelength division means 806 emits most of the interference light L4a to the optical fiber FB83a side and emits most of the interference light L4b to the optical fiber FB83b side. The wavelength division unit 807 emits most of the interference light L4a to the optical fiber FB84a side and emits most of the interference light L4b to the optical fiber FB84b side. The interference light L4a guided by the optical fibers FB83a and FB84a enters the interference light detection means 40a. The interference light L4b guided by the optical fibers FB83b and FB84b is incident on the interference light detection means 40b. The wavelength division means 806 and 807 function as the wavelength division means of the present invention.

  The subsequent configuration and operation of the interference light detection units 40a and 40b and the tomographic image processing unit 50 are the same as those in the first embodiment, and thus a duplicate description is omitted.

  Note that when the measurement light and the reference light are split at a branching ratio of 50:50 using a Michelson interferometer as in the optical tomographic imaging apparatus 800, as in the optical tomographic imaging apparatus 600 shown in FIG. A configuration in which the wavelength dividing means 5 is arranged downstream of the interferometer is also possible.

  In each of the above embodiments, the wavelength bands of the light La and Lb emitted from the light source unit have been described using an example in which they partially overlap, but the present invention is not limited to this, and the light La is not limited thereto. The wavelength bands of Lb and Lb may be discrete. In such a case, measurement is performed by analyzing the frequency of the interference signal ISa photoelectrically converted by the interference light detection means 40a and the interference signal ISb photoelectrically converted by the interference light detection means 40b by the broken image processing means. Intermediate tomographic information (reflectance) ra (z), rb (z) at each depth position of the object S is detected, and the tomographic image of the measuring object S is detected using the intermediate tomographic information ra (z), rb (z). Just get it. Specifically, the tomographic image processing means first detects the intermediate tomographic information ra (z) based on the light beam La by performing frequency analysis on the interference signal ISa, and performs intermediate analysis on the light beam Lb by performing frequency analysis on the interference signal ISb. Fault information rb (z) is detected, and average value r (z) = (ra (z) + rb (z)) / 2 of intermediate fault information ra (z) and rb (z) at each depth position Z is obtained. calculate. Thereafter, a tomographic image may be generated using the tomographic information r (z).

  In each of the above embodiments, the light receiving elements of the interference light detection means 40a and 40b are selected from, for example, an InGaAs photodiode or Si photodiode according to the wavelength band of the light La and the wavelength band of the light Lb. can do.

  Conventionally, it is a device configuration that must cover the entire wavelength range of light emitted from the light source unit with a single photodetector, and is used for light of the wavelength band λa and wavelength band λb as described above. Since there was no possible photodiode, a device capable of measurement with the combination of the wavelength bands of λa and λb as described above could not be constructed. However, according to the optical tomographic imaging apparatus of the present invention, since a plurality of interference light detecting means are provided so that each light can be detected, it is possible to perform measurement using a combination of the above-described wavelength bands of λa and λb. become. Since the light emission process of the semiconductor laser used for the light source and the light reception process of the photodiode used for the photodetector are based on the same principle, the light in the emission band of the semiconductor laser made of a certain medium is emitted from the photodiode made of the same medium. It can be detected. Therefore, by using both in pairs, it is possible to cover and measure all the wavelength bands that can emit light.

In addition, in the configuration of the optical tomographic imaging apparatus having a plurality of interferometers as shown in FIGS. 10, 11 and 14, the circulator 4a of the interferometer to which light in the wavelength band Δλa is incident is provided as BIG (Bi ₃ Fe ₅ O _12). ), It is desirable to use YIG (Y ₃ Fe ₅ O ₁₂ ) for the circulator 4b of the interferometer on which light in the wavelength band Δλb is incident. Conventionally, the device configuration has to cover the entire wavelength range of the light emitted from the light source unit with one circulator, so that the absorption loss is large in any wavelength range, and the light utilization efficiency is greatly reduced. There was a problem. However, according to the optical tomographic imaging apparatus shown in FIGS. 10, 11 and 14, since the interferometer is provided for each light, the above problem can be solved.

Alternatively, when the center wavelength of the sweep wavelength band is 1.0 μm, it is desirable to use TGG (Tb ₃ Ga ₅ O ₁₂ ) for the circulator. In the conventional technology, the optical tomographic imaging apparatus according to the embodiment of the present invention is not limited to the circulator, but the coupler, the dichroic mirror, the fiber, or the like needs to support the entire use wavelength range. Therefore, the required use of the optical component to be used can be relaxed, and the cost of the component can be reduced.

  The optical tomographic imaging apparatus of the present invention is not limited to the above wavelength band, and the wavelength band to be used can be changed as appropriate depending on the composition of the measuring object S. For example, light in a wavelength band with a small interaction with the measurement target S (for example, a 1000 nm band with little influence of water dispersion) and light in a wavelength band with a large interaction with the measurement target (for example, a 800 nm band) are combined. Thus, high-resolution tomographic image information can be obtained, and spectral information such as absorption characteristics, dispersion characteristics, and fluorescence characteristics of the measurement object can be measured simultaneously.

  When the optical tomographic imaging apparatus of the present invention is applied to an endoscope, if the wavelength band within the sensitivity of the CCD equipped in the endoscope, for example, light having a center wavelength of 850 nm is used as the light of the combined light source, It can also be used as aiming light, and it is not necessary to provide an aiming light source separately.

  The two lights emitted from the light source units of the optical tomographic imaging apparatuses of the first to ninth embodiments have different wavelength bands. Conventionally, an ideal light source used in an OCT apparatus has a Gaussian spectrum. In the TD-OCT apparatus, when a light source having a spectral shape deviating from a Gaussian shape is used, there is a problem in that the resolution of an image deteriorates because a side lobe stands. In the FD-OCT measurement for measuring a spectrum signal, a process of approximating a signal obtained when the spectrum is a Gaussian spectrum by measuring a light source spectrum in advance and applying a filter function obtained therefrom to an interference signal is conventionally performed. Has been done. However, the light source spectrum corresponding to the depth range from which the tomographic image is acquired must be continuous. For example, it is said that appropriate processing cannot be performed on a discrete spectrum waveform in which the light amount is zero in the middle of the emission band. It was.

  Further, in the conventional OCT apparatus, it has been desired that the wavelength band of the light source is wide in order to realize high-resolution measurement. As a light source, a semiconductor light source such as an inexpensive and small super luminescence diode (SLD) or a semiconductor optical amplifier (SOA) is desirable. However, since the gain band is limited by the characteristics of the medium, the light source continuously exceeds 100 nm. Realizing bandwidth is difficult.

  In view of this, there has been considered a method of combining light from a plurality of light sources as shown in Patent Document 1 to widen the wavelength band. Among them, there is a method of multiplexing light emitted from a plurality of light sources using a coupler with a branching ratio of 50:50. However, since the output of the coupler is half of the total of both, the light use efficiency is deteriorated. End up. There is also a method of multiplexing using a polarizing beam splitter, but this method can combine up to two lights.

  That is, in the Fourier transform method in the OCT measurement, the light source spectrum needs to be continuous and broadband, so that the light source unit 10 that emits discrete light La and Lb is a conventional OCT as a light source for acquiring a tomographic image. It has been thought that it is not suitable as a light source.

  However, as described in the first embodiment of the present invention, even when the light source unit 10 that emits a plurality of lights La and Lb having different wavelength bands instead of a wide wavelength band is used, high resolution is achieved. It was found that tomographic images can be obtained. For this reason, it is not necessary to use the light source unit limited to the specific characteristics as described above. Further, since the tomographic image processing means 50 generates a tomographic image from the reflection intensities of two interference lights having different wavelengths, a tomographic image having no side lobe can be acquired even when a light source having a discontinuous spectrum is used. And a high-resolution image can be obtained.

  In addition, since a high-resolution tomographic image can be obtained using a plurality of lights having different wavelength bands, a high-resolution type using a large number of lights and an inexpensive low-resolution type using a small number of lights. Switching is possible, and measurement according to demand is possible.

  Note that the optical tomographic imaging apparatuses of the first to eighth embodiments and the modifications are all SS-OCT apparatuses, and as described in the background section, the measurement rate is higher than that of the SD-OCT apparatus. This is advantageous. Specifically, for example, when an OCT apparatus having a wavelength band of 200 nm and a wavelength resolution of 0.1 nm is considered, in order to obtain a tomographic image with high resolution and optical image quality, more than 2000 data points are required, and more accurate. In order to know the correct spectrum shape, a data score of 4000 points or more is desirable. In addition, it is desirable for the OCT apparatus to display a two-dimensional tomographic image as a moving image. For example, an image with 2000 data points in the measurement wavelength band and 1000 lines in the direction perpendicular to the optical axis is displayed at a repetition rate of 10 Hz. In this case, a data read rate of 20 MHz is required.

  As described above, in the SD-OCT apparatus, in order to increase the number of data points, it is necessary to increase the number of detector elements. As a currently available detector array of InGaAs elements having light receiving sensitivity in the near-infrared region, which is a general light source wavelength in an OCT apparatus, there are 1024 elements (for example, Sensors Unlimited Inc., model number SU-LDV). -1024LE), which are expensive. In order to acquire the number of data points of 2000 points or more, or 4000 points or more, it is necessary to connect and use at least two detector arrays having 1024 expensive elements, preferably four or more. Further, when connecting a plurality of detector arrays, highly accurate position adjustment is required. Furthermore, when comparing the specifications of the above-mentioned detector array with 1024 elements and a detector array with 512 elements (sensors unlimited Inc., model number SU-LDV-512LD), the maximum line rate is 512 elements. In this detector array, it is 12820 frames / second, whereas in a detector array with 1024 elements, it is 4266 frames / second, and the read rate of one line decreases as the number of elements increases. Such a decrease in the readout rate of one line is a problem in that the frame rate of the image is decreased.

  On the other hand, in the SS-OCT apparatus, the increase in the number of data points can be realized at low cost by increasing the sampling interval of the detector. In the above example, when an image of 1000 lines perpendicular to the optical axis is displayed at 10 Hz, data may be acquired at a sampling rate of 40 MHz even when the number of data points is 4000. This is a level that can be sufficiently realized with one photodiode and an inexpensive electric circuit.

  In the case of widening the measurement light, in the SD-OCT apparatus, it is necessary to change the optical design such as a wavelength dispersive element such as a grating in the interference light detection means and a condensing element such as a lens. In the SS-OCT apparatus, Since it is only necessary to add a WDM coupler and a detector, this can be realized easily.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible unless it changes the summary of invention. For example, although an example in which one light is emitted from one gain medium has been described in the above example, a multicolor light source in which a plurality of lights having different wavelengths are emitted from one gain medium may be used. In this case, for example, the light source unit 10 of the optical tomographic imaging apparatus shown in FIGS. 10, 13, 15, and 16 may be replaced with a multicolor light source.

  In the above example, an example using two lights has been described in order to simplify the description, but three or more lights may be used. In the case of using n pieces of light, for example, an n × 1 WDM coupler or a plurality of WDM couplers can be used. FIG. 17 shows a case where two 2 × 1 WDM couplers 15 and 16 and one 2 × 2 WDM coupler 17 are used when n = 4 using light emitted from four wavelength swept light sources 1 to 4. A configuration example for multiplexing is shown. FIG. 18 shows a configuration example in which light is emitted from four wavelength swept light sources 1 to 4 and multiplexed by one 4 × 1 WDM coupler 18 when n = 4.

  Or you may employ | adopt the structure which makes the light source described in patent document 3 and patent document 4 one set, and combines several sets of light sources.

  In each of the above embodiments, the fiber ring type wavelength swept light source is used as the light source unit. However, a wavelength swept light source having another configuration may be used. For example, a diffraction grating, a polygon, or a band pass filter may be used as the wavelength selection unit. A wavelength scanning light source using a rare earth doped fiber or the like as a gain medium is also applicable. The wavelength sweep is preferably a continuous sweep, but may be a discontinuous wavelength change. Further, the wavelength sweep time of each light may be different from each other.

  In the above-described embodiment, the spectrum of light emitted from the light source unit is described as an example having a substantially Gaussian shape. However, the present invention is not limited to this. For example, the spectrum has a constant light intensity with respect to the wavelength. There may be.

  The emission wavelength range of one light source is not limited to the illustrated wavelength width, but it needs to be equal to or greater than a predetermined wavelength band that allows OCT measurement with a single light source. There is no clear boundary value for the predetermined wavelength band, but a system with a resolution of approximately 1 mm or less is assumed, and the frequency band of light is on the order of several tens of GHz or more.

  In the above embodiment, an example is shown in which light is guided by an optical fiber and multiplexed / demultiplexed by an optical coupler or a WDM coupler, but spatially multiplexed / demultiplexed by a mirror, prism, dichroic mirror, dichroic prism, or the like. A bulk optical system may be used. In addition to the WDM coupler and the dichroic mirror, the wavelength division and wavelength multiplexing means may be configured using a diffraction grating. Instead of the optical fiber probe, a configuration in which the spatially propagated light is scanned by a galvanometer mirror may be used.

  Further, in the above embodiment, the case where light reflected or backscattered from a measurement target is measured has been described as an example. In order to derive distribution, thickness distribution, birefringence, and the like, transmitted light may be measured instead of reflected light. In such a case, the transmitted light may be guided to the multiplexing means instead of the reflected light, and the transmitted light and the reference light may be combined, and the other configurations and methods in the above embodiment are not changed. Applicable.

1 is a schematic configuration diagram of an optical tomographic imaging apparatus according to a first embodiment of the present invention. The figure which shows the mode of the wavelength sweep of the light source unit of FIG. Is a diagram showing a spectrum of light emitted from the light source unit of FIG. Block diagram showing an example of the tomographic image processing means of FIG. Graph showing an example of interference light detected by the interference light detection means of FIG. The figure which shows the tomographic information of each depth position when carrying out the frequency analysis of the interference light detected in the interference light detection means of FIG. The figure for demonstrating the operation | movement of the 1st Embodiment of this invention. Schematic configuration of optical tomographic imaging apparatus according to second and third embodiments of the present invention The figure for demonstrating the operation | movement of the 2nd Embodiment of this invention. The figure for demonstrating the operation | movement of the 3rd Embodiment of this invention. Schematic configuration diagram of an optical tomographic imaging apparatus according to a fourth embodiment of the present invention. Schematic configuration diagram of an optical tomographic imaging apparatus according to a fifth embodiment of the present invention Diagram for explaining Fizeau interferometer Schematic configuration diagram of an optical tomographic imaging apparatus according to a sixth embodiment of the present invention Schematic configuration diagram of an optical tomographic imaging apparatus according to a seventh embodiment of the present invention Schematic configuration diagram of an optical tomographic imaging apparatus according to an eighth embodiment of the present invention Schematic configuration diagram of an optical tomographic imaging apparatus according to a ninth embodiment of the present invention The figure which shows the example which combines the light from four light sources The figure which shows another example which multiplexes the light from four light sources

Explanation of symbols

2 Multiplexing means 3, 3a, 3b Light splitting means 4, 4a, 4b Circulators 5, 5a, 5b Wavelength splitting means 6a, 6b Multiplexing / splitting means 7, 7a, 7b Optical path length adjusting means 10, 20 Light source units 10a, 10b , 20a, 20b Light source 30, 430 Probe 40a, 40b Interference light detection means 50, 55 Tomographic image processing means 60 Display device 100, 200, 250, 300, 400 Optical tomographic imaging device 500, 600, 700, 800 Optical tomographic image 705, 806, 807 Wavelength division means ISa, ISb Interference signal La, Lb Light L1a, L1b Measurement light L2a, L2b Reference light L3a, L3b Reflected light L4a, L4b Interference light S Measurement object Δλa, Δλb Wavelength band

Claims (10)

A first light source that emits first light whose wavelength is repeatedly swept within a first wavelength band, and a wavelength that is repeatedly swept within a second wavelength band that is different from the first wavelength band. A light source unit having a second light source that emits second light, wherein a part of the sweep of the first light and a part of the sweep of the second light are performed simultaneously;
Light splitting means for splitting the first light and the second light into first and second measurement light and first and second reference light, respectively;
The first and second reflected light and the first and second reflected light that are reflected from the measurement object when the measurement object is irradiated with the first and second measurement lights divided by the light dividing means A combining means for respectively combining the reference light of
First interference light detection means for detecting, as a first interference signal, first interference light generated when the first reflected light and the first reference light are multiplexed by the multiplexing means;
Second interference light detection means for detecting, as a second interference signal, second interference light generated when the second reflected light and the second reference light are multiplexed by the multiplexing means;
An optical tomographic imaging apparatus comprising: a tomographic image processing unit configured to generate a tomographic image of the measurement target using the first and second interference signals detected by the first and second interference light detection units. There,
The reflected light or the interference light from the measurement object is emitted to the first interference light detection means side when the wavelength of the reflected light or the interference light is within a third wavelength band, When it is within a fourth wavelength band that is distant from the third wavelength band, the light is emitted to the second interference light detection means side, and the second wavelength band between the third wavelength band and the fourth wavelength band is emitted. 5 having a wavelength division unit that emits light to the first interference light detection unit side and the second interference light detection unit side,
The first wavelength band and / or the second wavelength band includes at least a part of the fifth wavelength band, and the tomographic image includes the first light source and the second wavelength band. While light having a wavelength within the fifth wavelength band is emitted from one of the light sources, only the first interference signal or the second interference signal based on the light emitted from the one light source An optical tomographic imaging apparatus characterized by being generated using   The tomographic image processing means emits from one of the first light sources and the second light source as an interference signal while light having a wavelength in the fifth wavelength band is emitted from one of the first light sources and the second light source. 2. The optical tomographic imaging apparatus according to claim 1, wherein only the interference signal based on the light being used is used.   Light emitted from the one light source while the interference light detection means emits light having a wavelength within the fifth wavelength band from one of the first light source and the second light source. 2. The optical tomographic imaging apparatus according to claim 1, wherein only the first interference signal or the second interference signal based on the first interference signal is detected.   While the light source unit emits light having a wavelength within the fifth wavelength band from one of the first light source and the second light source, only the one light source emits the fifth wavelength band. The optical tomographic imaging apparatus according to claim 1, wherein the optical tomographic imaging apparatus emits light having a wavelength within the range.   While the light source unit emits light having a wavelength within the fifth wavelength band from one of the first light source and the second light source, light is emitted only from the one light source. The optical tomographic imaging apparatus according to claim 4, wherein the optical tomographic imaging apparatus is provided.   The light source unit emits light having a wavelength in the third wavelength band from the first light source and light having a wavelength in the fourth wavelength band from the second light source at the same time during a predetermined time period. While the light having the wavelength in the fifth or fourth wavelength band is emitted from the first light source, the light is emitted only from the first light source, and the first light source emits light. The light is emitted only from the second light source while light having a wavelength within the fifth or third wavelength band is emitted from the second light source. Optical tomographic imaging device.   The optical tomographic imaging apparatus according to claim 1, wherein a part of the first wavelength band and a part of the second wavelength band overlap each other.   The tomographic image processing unit connects the first interference signal and the second interference signal obtained by the first interference light detection unit and the second interference light detection unit and having a part of overlapping wavelength bands. 8. The optical tomographic imaging apparatus according to claim 7, wherein one interference signal is formed and a tomographic image is generated based on the interference signal.   9. The optical tomographic imaging apparatus according to claim 1, wherein the wavelength division means is a wavelength division multiplex coupler.   10. The optical tomographic imaging apparatus according to claim 1, wherein the light splitting unit and the multiplexing unit are provided for each of the first light and the second light. 10. .

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